T+3 stock settlement time

I have searched for an answer to this question but have not been successful. Suppose I bought 100 MSFT on Tuesday March 9th. On Friday, March 12th, the trade will settle. At what time does the trade settle on the 12th? Before the open? At the close? If you can provide a reference, that would be great.

I assume that no matter when I bought this MSFT stock on the 9th (whether it was pre-market, normal market, or post-market), it will settle at the same time on the 12th. Is this a correct assumption?